Where to find long term care for mentally disabled sister?

Just to chime in on group homes - my best friend opened her own group home based around her disabled daughter whom they could not care for at home. After a while my friends had five group homes but now is down to three because it was never her intention to have a group home dynasty. Her group homes are amazing - beautifully decorated, well-kept, good staff and lots of extras / she even takes the residents on an annual trip to Disneyland! She has told me when I'm ready she'll open a group home around my son if I don't like the mix of residents at a current home or there isn't an opening. You may not find something as accommodating as I have but there are nice places- you may just need to spend a bit of time vetting - and then of course, work to get your sister on board.

Thank you all for your thoughtful responses. I agree the best option for all is a group home. The problem? My sister flat out refuses to go. It was brought up once, hypothetically, and she threw a huge fit & told me she's not leaving. I'm thinking her attitude is based on fear of the unknown. I am trying to find a therapist for her that will make home visits and try to ease her into the idea. Wish me luck :-/

My mother died in 1962 and made my father promise never to institutionalize my sister who was 8. There were no group homes back then, just huge state facilities. They were horrific places. Sis remained at home until age 25. By then Dad was 60. He got involved with people who were establishing group homes. These were places with no more than ten residents, non-profit, with at least 2 staff on at night and more during the day to help dress, feed and transport clients to programs. He got her into one of the first houses that opened. She developed a sense of independence. She had friends, even a boyfriend here and there.
Today she is 61, lives in an airy ranch built from the ground up to be a group home. Full air conditioning there helps control behaviors and minimize seizures. She has a generous PNA, about $120 a month. Staff takes her shopping seasonally for clothes. She goes for a manicure monthly, sees the podiatrist monthly, gets free admission to events and performances due to her disability. If she needs anything "My staff takes care of that."
What's so bad about that? You go to work. She has staff.

Group homes are not necessarily bad places; even the Human Development Centers we have here in Arkansas are very good for some people though they have a bad rep. Talk to social services people and independent living centers about various suportive living arrangements that can be made - possibly it could even be outside care in her own home. Possibly medications can be tried that will help her with the OCD and anxiety. Yes, your parents made her eventual adjustment much harder than it could have been.

I don't have much experience with this issue but there are others here who have. Hopefully they will chime in.

My older brother had many problems, lived with my parents till he died suddenly at age 60, and I was very worried that I would be takeing care of the three of them. I had your same concern.

If he had outlived my folks I was planning on setting up a trust for his care from my parents estate. He would have most likely ended up in a group home and later a skilled nursing facility and at some point on Medicaid.

This is difficult, I was not close to my brother but felt duty bound to see he was taken care of. He probably would not have agreed or liked my plans for him but there was no way he could have taken care of an old house and five acres of land. And due to our history there was no way he was moving in with me.

As difficult as it may be you will have to do what has to be done. My guess is your sister may adjust to a group home in time. Good luck to you.